[Optimusglen]

I only have experience with one engine, so this may not be normal, but my mains looked great and my rod bearings had wear.

If you split the case first you need to get everything inspected. If the crank is within spec you don't need to have it reground. If there aren't scratches you don't need to have it polished. If your crank is warped or really worn it's a better idea to buy a different crank that's in spec, sure you could get it machined for oversized bearings, but then you have to also buy oversized bearings (including #8, which is quite expensive) and pay for the machine work. Probably cheaper to just get a new crank that's in spec.

For mag cases I've read that often times the years of heat cycles will mushroom the mating surfaces slightly, so several aspects of the case must be inspected. Aluminum cases don't have those issues I don't think.

The rod bolts are stretch bolts, they stretch slightly once they reach final torque. So once you remove them they are garbage. New ones are something like $15 each from our forum sponsor. So, 15x12 is $180 right there.

Bearings wear, sure you can measure them and if they are in spec with no scratches or copper showing you could probably reuse them if you must, they're cheap enough that replacing them just makes sense though. Main and rod bearings are probably another $150-$180 on the cheap end. And don't forget about the intermediate shaft bearings.

If the oil looks good, and you weren't having issues before, and you know the actual mileage and have service history, etc etc, I would leave the bottom end alone. Check the cylinder base decks to ensure they're aligned and move on. If you have any sort of issues, like weeping split line, I'd tear it down.